PS 5-45
Mapping potential microrefugia in rugged terrain
Although numerous studies report that climate change-induced range shifts are already underway for many species, there is growing concern that some species will be unable to keep pace with rapid climate change. Of particular concern are slowly dispersing and reproducing species whose life histories are incompatible with rapid migration. Avoiding local extinction could depend on availability of microrefugia, which are small, isolated populations with locally favorable microenvironments that allow species to survive outside their main distribution until favorable climates return. Microrefugia are more likely to exist in rugged terrain where topographic heterogeneity provides a diverse mosaic of microenvironments. The purpose of this study is to identify potential microrefugia (z-score < 2) using statistically downscaled fine-resolution (30 m) grids of historic (1951-2010) and future (2011-2099) climate in the Tehachapi Mountains, California. We used a range of climate change scenarios in the IPCC Fifth Assessment. We analyzed grids of average July maximum temperature and water-year-accumulated climate water deficit to locate the coolest, wettest areas of the landscape.
Results/Conclusions
Cool microenvironments were consistently found only at the highest elevations (> 2000 m), partially due to the inability of air temperature maps to account for finer-scale temperature variability at the ground surface. Wet microenvironments were more scattered, occurring at elevations as low as 750 m under the driest model (MIROC RCP 8.5), predominantly on north-facing aspects. These areas currently support locally rare species, including white fir (Abies concolor) and sugar pine (Pinus lambertiana). As emissions increased, we found generally fewer and smaller potential microrefugia across climate models, though with a few exceptions. In addition, warm and dry microenvironments will increase in size and frequency in the future, potentially acting as stepping stones for previously absent species to advance into the landscape. We note that even at 30 m resolution, our climate grids were unable to detect narrow riparian areas, which may harbor species despite regionally unfavorable climate owing to increased soil moisture. Further, by simply mapping potential microrefugia, we are unable to predict true biological responses to climate change. Nonetheless, our results suggest that long-term, fine-resolution climate grids can be important tools in identifying potential microrefugia to inform regional conservation planning and prioritization.